Plan meta-objective for sub-micron quantitative phase imaging.

Quantitative phase imaging (QPI) provides valuable objective insights for investigating transparent samples, yet miniaturizing QPI systems without compromising performance remains a critical challenge for applications requiring compactness and portability. Here, by introducing partially coherent illumination modulation, together with a plan meta-objective (PMO) design, we present a compact QPI system with sub-micron resolution. The PMO is a monolithically integrated doublet metalens with its dispersion enabling focal shifts at two wavelengths, obviating the need for mechanical translations during image acquisition for phase retrieval. The PMO is also optimized to correct for monochromatic aberrations, delivering an object-side field of view equivalent to ~90% of the lens aperture with minimal distortion and aberrations. The spatial coherence of the illumination is controlled to enhance imaging resolution. By co-designing illumination and imaging systems, we demonstrate QPI achieving a half-pitch lateral resolution of 488 nm with a phase accuracy of 0.06λ. Our approach enables high-quality QPI analysis of diverse phase objects, including unstained biospecimens, laying the foundation for the development of compact, stable, and practical QPI platforms.